1. Field of the Invention
The present invention relates to a polarization converting system, a method of manufacturing the same and a liquid crystal display using the same, and more particularly, to a polarization converting system that can reduce a light loss caused by a misalignment of a polarization splitting unit and a polarization converting unit, a method of manufacturing the polarization converting system and a liquid crystal display using the polarization converting system.
2. Description of the Related Art
In a current liquid crystal display (LCD), only about 5% of total light flux emitted from a light source is used as effective light. Absorption of light by both color filters and absorbing polarizers is the number one cause of the deterioration of the light efficiency.
In an LCD panel, as absorbing polarizers disposed on both sides of a liquid crystal layer basically absorb 50% of incident unpolarized light, studies for improving the light efficiency by replacing the polarizing plates or converting most of the light incident on the polarizing plates into polarized light in parallel with transmission axes of the polarizing plates have been actively done.
One of the studies is to split incident unpolarized beam into two rays of linearly polarized light using a hologram device or a polarizing beam splitter (PBS) and rotate one linearly polarized light by 90 degrees by selectively providing a half wave plate on the one linearly polarized light path, thereby converting all of the light incident on the LCD panel into specific linearly polarized light. As a result, by eliminating the light absorption by the absorbing polarizers, the light efficiency can be improved. As described above, a system including the PBS and half wave plate for converting the polarization of the all of the light into the specific polarization is called a polarization converting system.
FIG. 1 schematically illustrates a polarization converting system disclosed in Japanese Laid-Open Patent No. 2004-272106.
Referring to FIG. 1, the polarization converting system includes first and second light transmission members 1 and 5 respectively having inclined portions 3 and 7 of which sections are formed in a triangular shape and of which inclined surfaces 3A and 7a are spaced apart from each other by a predetermined gap to be aligned in an identical direction, first and second polarization splitting films 2 and 6 respectively formed on the inclined surfaces 3A and 7a, half wave plates 9 formed on a first surface of the first light transmission member 1 to correspond to the inclined portions 3 formed on a second surface opposite to the first surface, and light shielding members 8 formed on a first surface of the second light transmission member 5 to correspond to the inclined portions 7 formed on a second surface opposite to the first surface.
In the related art polarization converting system, unpolarized light incident on regions between the light shielding members 8 is split by the first polarization splitting films 2 formed on the inclined portions 3 of the first light transmission member 1. P-polarized light passes through the first polarization splitting films 2 and is converted into S-polarized light by the half wave plates 9. The S-polarized light is reflected from the first polarization splitting films 2 to the second polarization light splitting layers 6 formed on the inclined portions 7 of the second light transmission member 5 and is further reflected on the second polarization splitting films 6 to travel in a direction identical to that of the P-polarized light passed through the first polarization splitting films 2.
When the above-described related art polarization converting system is used, unpolarized light can be converted into specific linearly polarized light.
However, in the related art polarization converting system, since the half wave plates 9 must be installed to correspond to the first polarization splitting films 2 provided on the inclined portions 3 of the first light transmission member 1 through a special process, there may be a misalignment between the half wave plates 9 and the first polarization splitting films 2. The misalignment may cause the deterioration of the polarization converting efficiency. For example, when the half wave plates 9 are deviated from optimum locations relative to the corresponding first polarization splitting films 2, a part of the P-polarized light passed through the first polarization splitting films 2 does not passed through the corresponding half wave plates 9 but travels as it is and a part of the S-polarized light reflected from the first and second polarization splitting films 2 and 6 passes through the corresponding half wave plates 9 to be converted into the P-polarized light. As a result, the light emitted from the related art polarization converting system may partly include undesired P-polarized light, thereby deteriorating the polarization converting efficiency.
Furthermore, in order to prevent the misalignment between the first polarization splitting films 2 and the corresponding half wave plates 9 when manufacturing the related art polarization converting system, a precise aligning process is required, thereby increasing the manufacturing costs.